Auxiliary air regulator for furnaces



June 1934.

D. F. HUNT ET AL AUXILIARY AIR REGULATOR FOR FURNACES Filed Nov. 9, 1951 3 Sheets-Sheet l .9 p h J 4 a M 1 w 3 w I i n n "if" E h L of R 4 M w WW1 Z7 jam?! FJhmf ENTO 0 iii amEfissmarz ATTORNEYS BYWWF June 12, 1934. D. F. HUNT ET AL AUXILIARY AIR REGULATOR FOR FURNACES Filed Nov. 9, 1931 3 Sheets-Sheet 2 INVENTORY .Du rliP/ 1 /'[u u i [117111 0121 1 0832120 BY g fl A TTORNE Y3 June 12, 1934.

D. F. HUNT ET AL AUXILIARY AIR REGULATOR FOR FURNACES Filed Nov. 9, 1931 3 Sheets-Sheet 5 \IQQQQ I alanib INVENTOR 2472141311 uni Patented -lune 12, 1934 UNITED STATES PATENT OFFICE AUXILIARY AIR REGULATOR FoR FURNACES tion of Delaware Application November 9, 1931, Serial No. 573,858

2 Claims.

This invention relates to a furnace in which air is fed directly into the combustion chamber above the fuel bed (as well as under and through the fuel bed) so as to cause a complete combustion of the distilled volatile gases which would otherwise arise unburned from the upper layers of the fuel bed. In particular, the invention relates to the hand fired furnaces of lime kilns, which are intermittently supplied with fuel by reason of the nature of the firing.

The direct object of the invention is to produce a higher grade of unslacked lime or quicklime and at a lower cost. The object in general of the invention is to thoroughly consume all of the fuel in the most efficient manner and to produce gases of combustion of uniform temperature and quantity. Numerous other objects of the invention and practical solutions thereof are disclosed in detail in the herein patent specification wherein:

In the accompanying drawings;

Figure 1 is a front elevation of furnace adapted .to supply hot gases of combustion to a lime kiln.

Figure 2 is a vertical, longitudinal section thereof taken on line 2-2 Fig, 1.

Figure 3 is an enlarged, fragmentary top plan .thereof showing the mechanism which controls the auxiliary air shutter.

Figure 4 is a horizontal section through the furnace and a part of the lime kiln taken on line 4-4, Fig. 1.

Figure 5 is an enlarged, fragmentary, vertical, longitudinal section through the air shutter controlling mechanism taken on line 5-5, Fig. 3,

Figures 6 and '7 are enlarged, vertical, trans,- verse sections through said air shutter controlling mechanism taken on correspondingly num- Ebered lines of Fig. 5.

i-Fig. 8 is a front elevation of a modified form of the invention.

In the following description similar characters of reference indicate like parts in the sevieral figures of the drawings.

Our invention may be embodied in various forms and in auxiliary air regulators for furnaces of different constructions, and the present applications are therefore to be regarded merely as some of the possible organizations which satisfactorily carry out the invention in practice. As here shown, the same (referring for the present to Figs. 1-7) is constructed as follows:

Figure 2 illustrates a typical form of Dutch oven furnace having front and rear walls 10 and 11; a combustion arch 12, underneath which is a combustion chamber; stationary grate bars l4; ash pit 15; fire door 16; and ash pit door 17, Fresh fuel 18 is hand fired through said fire door 16 and is deposited upon said grate bars 1%, the primary or main air being supplied; in the usual and well known manner, from the ash pit 15 up o through said grate bars and fuel bedfand the gases .of combustion from said fuel bed being sub-. jected to the intense radiant heat of thecome bustion chamber. From the latter the-gases of combustion pass through a combustion gas port 5 20 into the lower end of a lime kiln 21 which is filled with limestone rock 22. Said gases of combustion come into direct contact with the limestone rock 22 and, after the heating has been continued a sufliciently long period of time the carbon dioxide and water is entirely driven off from said limestone rock to produce calcium oxide.

In such installation it is more than usually important that the gases of combustion be clean, inasmuch as they come into direct contact with the final product of the lime kiln. The final product is calcium oxide and must be clean to properly perform its functions. In addition to this, it is important that the highest thermal effi- 30 ciency be obtained from the fuel which is burned.

It is also important that the gases of combustion be substantially uniform as to temperature and quantity, so as to obtain a product (calcium oxide) which is uniform and'high'i n plasticity, All .of these factors point toward the great desirability of having the fuel and its volatile gases completely oxidized and the temperature held uniform throughout the entire lime kiln heating cycle." Such a result has been successfully commercially obtained by the invention constituting the basis and present patent application. The construction shown in theaccompanying drawings is organized as follows:

Secured by stud bolts or otherwise to the front faces 10 of a row of furnaces are a plurality of pairs of horizontally and outwardly projecting bearing brackets 25, 251. In each pair of said brackets is journaled a short, horizontal worm 26, the opposite ends of which are connected (by 190 cotter pins 27 or otherwise) to a length of tubular shafting 28. The latter connects each of said worms 26 with the companion pair of worms immediately adjacent, so as, in effect, to provide a single long shaft A which drives all of said worms at an identical and preferably uniform rate of speed, the actuating means being a single source of mechanical power such as an electric motor or its equivalent.

Secured by bolts 30 and 300 to said brackets 25 and 251 are a pair of parallel, oppositely disposed guides 31 and 310 which are constructed of angle iron with their horizontal flanges cut away at opposite ends adjacent said brackets 25, 251. The central portion of said horizontal flanges which are not cut away constitute symmetrical guides 32, 320, the rear ends of which terminate in transverse alignment with the rear end of the threads of their companion worm 26, and the front ends of which overlap, in transverse alignment, the front end of the threads of said worm. Said worm threads are spaced inwardly from the inner faces of the brackets 25, 251,the intervening portions of said worm being turned down to a diameter equal to the root diameter of the worm threads to form the front and rear cylindrical hubs 33 and 331.

Adapted to engage with the upper half of the threads of said worm 26 is a gear toothed follower 34 the upper face of which is flat at its side portions to adapt the same to bear against the flat lower faces of the horizontal flange guides 32, 320. As long as said follower is in contact with said guides 32, 320, it is compelled to maintain a threaded engagement with the threads of the worm 26. As said worm continues to rotate, however, said follower 34 is caused (by reason of its threaded engagement with said worm) to be moved longitudinally rearward until finally it passes beyond the rear end of the thread of said Worm and slides out upon the rear hub 331. From this position no further rearward movement of said follower 34 can take place until the furnace operator (at the conclusion of the hand firing operation) lifts said follower 34 out bodily and moves it forwardly and drops it upon the front hub 33 and then allows it to be drawn under the front ends of the guides 32, 320, whereupon it again engages with the Worm threads and is again moved slowly rearwardly to the rear end of said worm thread.

Projecting upwardly from the central part of said gear toothed follower 34 is a bifurcated lug 35 to which is pivoted the front end of a chain belt 36 or other suitable flexible connecting means. This chain belt 36 passes over a pulley wheel 3'? (which is pivoted at 38 to the front face of the furnace) and thence passes downwardly and is connected to the upper end of an auxiliary air shutter 39, the weight of which is sufficient to at all times keep a light tension on said chain belt 36. This shutter 39 is suitably held against the front face 10 of the furnace by a pair of guides 40, and is adapted (by reason of its variable vertical position) to control the flow of auxiliary air through a companion auxiliary air feeding opening 41 which is formed in the front wall 10 of said furnace, and communicates by Way of a nozzle or nozzle-shaped opening 42 with the combustion chamber 13 of the furnace. The lowermost position of said auxiliary air shutter 39 is limited by a suitable stop 43 secured to the front wall 10 of the furnace, the vertical position of said stop 43 being such that when the lower face of said shutter 39 drops down upon said stop, the tension upon the chain belt 36 is relieved so as, at this time, to eliminate any cooking of the gear toothed follower 34 and its concomitant irregular frictional wear upon the rear worm hub 331.

Operation The fireman or operator of the furnace first shovels the required amount of green fuel 18 upon the grate bars 14. Air is fed up through the fuel bed from the ash pit in the usual and well known manner, and this regular supply of air is here (in the construction of Figs. 1-7) assumed to be relatively constant in amount, but this amount can in no case be sufficient to cause a complete combustion of the fuel so long as there is any green fuel on top of the fuel bed, as has been demonstrated by actual tests with variable ash pit air pressure. It has been found desirable, because of the fact, to feed auxiliary air directly into the combustion chamber above the fuel bed, this desirability being particularly pronounced during the period of time immediately following the covering of the incandescent fuel bed with green coal 18. It is at this time, therefore, that the greatest amount of auxiliary air should be fed into the combustion chamber. The accomplishment of such a desired result is obtained in a semi-automatic manner by the use of the herein invention, as follows: As soon as the fireman has finished his charging of the furnace, he lifts up the gear toothed follower 34 and moves it forwardly beyond the front end of the horizontal guides 32, 320 (see dotted lines, Fig. 5) and drops it upon the front hub 33 of th worm 25, and then slides it rearwardly under the front end of said guides 32, 320 against the front end of the threaded portion of said worm 26 (see full lines of Figs. 5, 1 and 3). This operation causes (in its entirety) the auxiliary air shutter 39 to be opened to its fullest extent. The fireman then closes the firing door 16.

The result of this manipulation of the follower 34 is that a maximum of auxiliary air is fed into the combustion chamber 13 at the time when a maximum of volatile gases are being driven off from the upper layers 13 of the fuel bed. It should be noticed that the distribution of this auxiliary air is relatively even over the fuel bed, the air entering through the auxiliary air feeding opening 41 and passing thence through the nozzle 42, the axis of which diagonal with respect to the combustion chamber 13. This arrangement insures an even distribution of auxiliary air over the fuel bed. noted that this feeding of auxiliary air above the fuel bed automatically causes the amount of vacuum in the combustion chamber to drop and to thereby decrease the differential in pressure between said combustion chamber 13 and 1- ash pit 15 and thereby decreasing the flow of normal (ash pit) air through the fuel bed. In other words, the greater amount of heat which is obtained as a result of the burning of the volatile gases with auxiliary air is counterbalanced at this particular time by a lessening of the heat which is obtained as a result of the combining of the air flow through the fuel bed with the fuel lying thereon. In this manner the temperature and quantity of combustion gases which are given off from the fuel bed is maintained fairly constant in amount,as a result of which the quality of the quicklime produced in the lime kiln 21 (particularly as to its plasticity) is very considerably increased, as comparedv to the hand fired lime kiln furnaces heretofore used.

As the volatiles in the green coal 18 are gradually oxidized, it is desirable to decrease gradually the amount of auxiliary air which is allowed to pass through the auxiliary air nozzle 42, and, as a result of which, to concomitantly increase the flow of air through the more or less incandescent fuel bed. In this regard it will be noted that the weight of the auxiliary air shutter It should also be I puts a tension on the chain belt 36 and that this causes the lower gear toothed face of the follower 34 to mesh with the worm thread of the worm 26 as shown in full lines in Figs. 1, 3 and 5. The worm 26 is, as heretofore described, being rotated from a suitable source of power at a constant rate of speed, and this causes the gear toothed follower 34 to be correspondingly moved rearwardly and longitudinally and the auxiliary air shutter 39 to be gradually lowered and the auxiliary air supply thus gradually reduced. Finally, by the time all of the volatile matter has been burned out of the green coal 18 and only pure carbon remains, the shutter 39 arrives at its lowermost position and all of the auxiliary air is out 01f. What the exact period of time is during which auxiliary air should be fed to the combustion chamber 13 depends upon such variables as the kind of fuel, thickness of fuel bed, etc., and this variable factor is adjusted by suitably regulating the speed of the motor which drives the entire worm shaft A. It is to be understood that an interval of time may elapse subsequent to the closing of said auxiliary shutter 39 and the feeding upon the fuel bed of a supply of fresh green coal 18, but Whatever this may be, it has been found in actual practice that a firing interval of fifteen minutes for furnaces equipped in accordance with the herein invention, has given actual commercial results which are very much superior (as to the character and cost of the product) to lime as heretofore produced.

Dual air control (Fig. 8)

In Fig. 8 is illustrated a modified form of the invention in which the flow of air is positively controlled both directly into the combustion chamber above the fuel bed and also into the ash pit below said fuel bed (from whence said air passes up through said fuel bed). In this case the green fuel is fired into the combustion chamber precisely as heretofore described and the control of the air flowing directly into the combustion chamber above the fuel bed is likewise identical. This is accomplished by a worm 26a driven by a constantly rotating shaft Aa and actuating a gear toothed follower 34a connected with a chain belt 36a which gradually lowers the auxiliary air shutter 39a.

In this construction of Fig. 8, moreover, the primary air flow into the space below the grate bars is also positively controlled. This is accomplished as follows: Secured to the bifurcated lug 35a of aforesaid gear toothed follower 34a is a horizontal chain belt 361a which extends in a direction opposite to that of its companion chain belt 36a and passes around a grooved pulley 371a journaled at 381a on the front wall 10 of the shutter 39a.

furnace. Secured to the lower end of said chain belt 3610. is a primary air control shutter 39141 which is arranged in a pair of guides 401a similarly to the arrangement of the auxiliary air In actual practice the width of this primary air shutter 391a may be either greater or less than the width of the auxiliary air shutter 39a, this being a matter entirely dependent on the character of the fuel supplies, the type of grate bars, the area of the fuel bed, proportions of the combustion chamber, etc. It is preferred however that the height of both shutters be the same, although obviously even this may be different for the two shutters if overtravel of the shutters, slack cable or other expedients of design are resorted to.

The advantage of the construction of Fig. 8 is that the air is positively controlled both above and below the grate and that automatically the amount of air fed below the grate is increased in exact proportion to the amount which the air fed into the combustion chamber above the grate is being cut down. It is obvious that, as far as the operators work is concerned, the manual resetting of the gear toothed follower 34a is not appreciably more arduous than the resetting of the similar toothed follower 34 of Figs. 1-7.

We claim:

1. An auxiliary air regulator associated with the combustion chamber and fuel bed of a furnace and comprising means for feeding air to said fuel bed at a point below said fuel bed; an auxiliary air shutter located above said fuel bed and adapted to control the flow of air into said combustion chamber; a power driven shaft; a worm on said shaft; a gear toothed follower adapted to mesh with said Worm; and a guide adapted to hold said follower in contact with said worm, said guide being open at its opposite ends so as to permit disengagement of said follower from said worm.

2. An auxiliary air regulator associated with the combustion chamber and fuel bed of a furnace and comprising means for feeding air to said fuel bed at a point below said fuel bed; an auxiliary air shutter located above said fuel bed and adapted to control the flow of air into said combustion chamber; a power driven shaft; a worm on said shaft and having a smooth shouldered end; a gear toothed follower adapted to mesh with said worm; and an open ended guide adapted to hold said follower in contact with said worm and positioned adjacent said worm and extending over the smooth-shouldered end thereof.

WILLIAM E. HESSMAN. DANIEL F. HUNT. 

